Task e57facc2: Undo and live SSE updates in the admin PWA

- api/events.ts: fetch-based reader for GET /api/v1/admin/events (admin JWT
  in the Authorization header via apiFetch, never in the URL), an incremental
  SSE frame parser that buffers frames split across chunks and drops malformed
  frames, and bounded-backoff reconnect with a clean abort on stop.
- api/useTransitions.tsx: one stream per signed-in shell (TransitionsProvider
  in App) fanned out to screens; no provider means no stream.
- Today: Undo posts /instances/{id}/uncomplete, disables every Undo while in
  flight, shows a dismissible message on failure, and refetches the snapshot;
  any transition refetches in place. Mark done stays inert.
- History: quest transitions refetch the active filter in place; rows stay
  read-only.
- Tests for parsing, stream auth/teardown/reconnect, Undo, and live refetch.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

admin/src/history/HistoryTab.test.tsx

@@ -3,6 +3,8 @@ import { cleanup, fireEvent, render, screen, waitFor, within } from "@testing-li
 import HistoryTab, { FOOTER_NOTE, computeStats } from "./HistoryTab";
 import type { HistoryFilter, HistoryRow } from "../api/history";
 import { storeTokens } from "../auth/oidc";
+import { TransitionsProvider } from "../api/useTransitions";
+import { frame, testStream, type TestStream } from "../api/testStream";
 
 const TODAY = "2026-09-23";
 
@@ -423,3 +425,104 @@ describe("HistoryTab", () => {
     expect(screen.getByTestId("history-scroll").style.paddingBottom).toBe("92px");
   });
 });
+
+describe("HistoryTab live updates", () => {
+  let fetchMock: ReturnType<typeof vi.fn>;
+  let streams: TestStream[];
+
+  function historyRequests(): URL[] {
+    return fetchMock.mock.calls
+      .map(([url]) => new URL(String(url), "http://x"))
+      .filter((url) => url.pathname === "/api/v1/admin/history");
+  }
+
+  const PAYLOAD = {
+    child_id: 2,
+    child_name: "Maeve",
+    instance_id: 2,
+    quest_title: "Make bed",
+    window: "morning",
+    due_date: TODAY,
+    due_time: null,
+    occurred_at: "2026-09-23T15:10:00Z",
+  };
+
+  beforeAll(() => {
+    vi.stubEnv("TZ", "America/Los_Angeles");
+  });
+
+  afterAll(() => {
+    vi.unstubAllEnvs();
+  });
+
+  beforeEach(() => {
+    sessionStorage.clear();
+    storeTokens({ access_token: "at-123", expires_in: 600 });
+    streams = [];
+    fetchMock = vi.fn((url: string) => {
+      if (new URL(url, "http://x").pathname.endsWith("/api/v1/admin/events")) {
+        const stream = testStream();
+        streams.push(stream);
+        return Promise.resolve(stream.response);
+      }
+      return Promise.resolve(routeFetch(url));
+    });
+    vi.stubGlobal("fetch", fetchMock);
+  });
+
+  afterEach(() => {
+    cleanup();
+    vi.unstubAllGlobals();
+  });
+
+  it("a quest transition refetches the active filter; a day-complete does not", async () => {
+    render(
+      <TransitionsProvider>
+        <HistoryTab today={TODAY} />
+      </TransitionsProvider>,
+    );
+    await screen.findByTestId("stat-on-time");
+    fireEvent.click(screen.getByRole("button", { name: "Reversals" }));
+    await waitFor(() =>
+      expect(historyRequests().some((u) => u.searchParams.get("filter") === "reversals")).toBe(true),
+    );
+    await screen.findByTestId("stat-on-time");
+    await waitFor(() => expect(streams).toHaveLength(1));
+    const before = historyRequests().length;
+
+    streams[0].push(
+      frame("nestquest_child_day_complete", {
+        child_id: 2,
+        child_name: "Maeve",
+        quests_due: 4,
+        quests_completed: 4,
+        occurred_at: "2026-09-23T15:00:00Z",
+      }),
+    );
+    await new Promise((resolve) => setTimeout(resolve, 30));
+    expect(historyRequests().length).toBe(before);
+
+    streams[0].push(frame("nestquest_quest_uncompleted", PAYLOAD));
+
+    await waitFor(() => expect(historyRequests().length).toBe(before + 3));
+    const refetched = historyRequests().slice(before);
+    // One refetch (reversals + the two stats queries), same range and filter.
+    expect(refetched.map((u) => u.searchParams.get("filter")).sort()).toEqual([
+      "all",
+      "missed",
+      "reversals",
+    ]);
+    for (const url of refetched) {
+      expect(url.searchParams.get("start")).toBe("2026-09-10");
+      expect(url.searchParams.get("end")).toBe(TODAY);
+    }
+    await new Promise((resolve) => setTimeout(resolve, 30));
+    expect(historyRequests().length).toBe(before + 3);
+    expect(screen.queryByTestId("history-loading")).toBeNull();
+    expect(screen.getByRole("button", { name: "Reversals" }).getAttribute("aria-pressed")).toBe("true");
+    // Rows stay read-only (D-005): no row carries a control.
+    for (const row of screen.getAllByTestId("history-row")) {
+      expect(within(row).queryByRole("button")).toBeNull();
+    }
+  });
+});